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Energy Efficient Process Heating. Energy Balance on Furnace. Energy Saving Opportunities From Energy Balance. Reduce opening losses: radiation and air exchange Reduce cooling losses Reduce conveyance losses Reduce storage losses Reduce wall losses Reduce flue losses

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Presentation Transcript
energy saving opportunities from energy balance
Energy Saving Opportunities From Energy Balance
  • Reduce opening losses: radiation and air exchange
  • Reduce cooling losses
  • Reduce conveyance losses
  • Reduce storage losses
  • Reduce wall losses
  • Reduce flue losses
    • Improve internal heat transfer
    • Reduce air leakage into furnace
    • Control combustion air / oxygen
  • Reclaim heat
    • Pre-heat combustion air
    • Pre-heat load
    • Cascade heat to lower temperature processes
cover charge wells
Cover Charge Wells
  • 2 ft x 4 ft open charge well radiates and convects heat
  • Cover charge well with mineral fiber insulation 75% of time
  • Savings = $1,500 /yr
reduce conveyance losses
Reduce Conveyance Losses
  • Slow conveyor
    • Brazing oven at 1,900 F
    • Conveyor runs at 0.7 ft/min
    • Conveyor loaded 30% of time
    • Slow conveyor to 0.3 ft/min when unloaded
    • Reduces conveyor losses by 40%
reduce conveyance losses1
Reduce Conveyance Losses

Lighter conveyance fixtures reduce energy carryout losses

reduce storage losses
Reduce Storage Losses

Larger batch sizes to reduce number of loads in heat treat ovens

reduce storage losses1
Reduce Storage Losses

Reduce bricks (thermal mass) on transport cars

reduce storage losses2
Reduce Storage Losses

Increase batch sizes in arc furnaces

insulate hot surfaces
Insulate Hot Surfaces
  • Insulate four lids at 400 F
  • Induction furnace efficiency = 51%
  • Savings = $17,0000 /yr
flue losses
Flue Losses
  • Flue losses increase with:
    • Temperature
    • Flow
reduce flue losses1
Reduce Flue Losses
  • Reduce Temperature
    • Improve internal heat transfer
  • Reduce Flow
    • Reduce air leakage into furnace
    • Combustion air control
    • Use O2 instead of ambient air for combustion
convert batch cross flow processes to continuous counter flow
Convert Batch Cross Flow Processesto Continuous Counter Flow

Batch crucible melting Counter-flow cupola melting

replace reverb cross flow with stack counter flow furnace and pre heat charge
Replace Reverb (Cross Flow) with Stack (Counter Flow) Furnace and Pre-heat Charge

Reverb Furnace Stack Furnace

relocate exhaust ports to increase counter flow within zones
Relocate Exhaust Portsto Increase Counter-flow Within Zones

Increases convection heat transfer by 83%

Contact length = 2 x (5 + 4 + 3 + 2 + 1) = 30 feet

Contact length = (10 + 9 + 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1) = 55 feet

set exhaust dampers to increase counter flow in dry off oven
Set Exhaust Dampers to Increase Counter Flow in Dry Off Oven

Product In

Product Out

100% open 75% open 50% open 25% open 12% open

reduce air leakage
Reduce Air Leakage

Heat in

Flue Gases

Negative Pressure

Combustion Air

Air Leaks

Fuel

seal furnace openings
Seal Furnace Openings

Seal opening around lid with mineral fiber blanket

use draft control to balance pressure

Flue damper

Counterweight

Hydraulic cylinder

Hydraulic

power unit

Controller

Compensating line

Pressure tap

(not in line with

opposing burner)

Use Draft Control to Balance Pressure
combustion with air
Combustion with Air

Minimum Combustion Air (Stoichiometric):

CH4 + 2 (O2 + 3.8 N2) CO2 + 2 H2O + 7.6 N2

Excess Combustion Air:

CH4+ 4 (O2 + 3.8 N2) CO2 + 2 H2O + 15.2 N2 + 2 O2

excess combustion air de creases flame temperature and efficiency
Excess Combustion AirDecreases Flame Temperature and Efficiency

Air Preheat temperature)

% Available Heat

% Excess Air (% O2) in flue gases

Flue gas temperature)

combustion with oxygen eliminates unnecessary nitrogen
Combustion with Oxygen Eliminates Unnecessary Nitrogen
  • Combustion with Air
    • CH4 + 2 (O2 + 3.8 N2) > CO2 + 2 H2O + 7.6 N2
    • Mair / Mfuel= [ (4 x 16) + (4 x 3.8 x 14) ] / (12 + 4)
    • Mair / Mfuel= 17.6
  • Combustion with O2
    • CH4 + 2 O2 > CO2 + 2 H2O
    • Mo2 / Mfuel = (4 x 16) / (12 + 4)
    • Mo2/ Mfuel= 4.0
slide43

Combustion with Oxygen

Increases Efficiency

reclaim heat
Reclaim Heat
  • Preheat combustion air
  • Preheat load/charge
  • Cascade to lower temperature process
preheat combustion air with external recuperator1

ex. gas out

Th2 = 950 F

comb. air out

Tc2 = 615 F

comb. air in

Tc1 = 95 F

ex. gas in

Th1 = 1,465 F

Preheat Combustion Air with External Recuperator
pre heat load using counter flow
Pre-heat Load Using Counter-flow

Stack

Burners

Current Design

Recommended Design

cascade heat to lower temperature process
Cascade Heat to Lower-Temperature Process

High Temperature Oven Low Temperature Oven

voc destruction with thermal and catalytic oxidizers
VOC Destruction with Thermal and Catalytic Oxidizers
  • Reduce VOC Stream
  • Pre-heat VOC Stream with Recuperator
  • Pre-heat VOC Stream with Regenerator
  • Use Thermal Oxider Exhaust
reduce voc stream with carbon adsorber
Reduce VOC Stream with Carbon Adsorber
  • Inlet: 50,000 cfm with 50 ppm
  • Outlet: 5,000 cfm with 500 ppm (10x concentration)
  • Outlet (BAC): 50 cfm with 50,000 ppm (1,000x concentration)